Sometimes, but not always [although relatively often], Mellel will crash when typing accents, specifically é, into a footnote. This is a relatively new occurrence (since this spring) but I cannot be sure of exactly when it began. Because I write in French, English and Arabic transliteration, I use Unicode Hex Input rather than "option+" for accents. Copying the character carrying the accent doesn't cause any disruption nor does writing in the body of the document. Definitely a problem.